1. Technical Field
In a device for producing a box of a corrugated board sheet, the present invention relates to a method and device for producing a box of a corrugated board sheet in which box-producing precision and processing efficiency are enhanced by performing a box-producing process of a board sheet which is formed with a size of a plurality of corrugated board boxes and cutting the board sheet into a plurality of pieces each having a size of one corrugated board box.
2. Description of the Related Art/Background Art
A corrugated board sheet manufactured by a corrugator is processed for printing, creasing and slotting on a conveyance line of the box-producing machine, and then formed into a square tube in a gluing step and a folding step in which a gluing margin of one side panel of four panel box is overlapped and glued to another side panel to form a body in a shape of a square tube, and flaps extending from each panel form a bottom part and a top part of the box.
FIG. 5 illustrates a general structure of a box-producing line of the corrugated board box. In FIG. 5, the box-producing line starts from the right side and the corrugated board sheet S is conveyed in a direction of arrow a so as to conduct the box-producing process. In the upstream of the box-producing process, front and back linerboards and a corrugated board sheet S of a corrugating medium to be interposed between the linerboards, are produced and stacked in a paper supply part A. In this, the corrugated board sheet S is trimmed in the corrugator line and short ends and long ends are cut into a predetermined size and also the creasing in a longitudinal direction (crease lines b) is done.
In the paper supply part A, the corrugated board sheets S are positioned in the same direction and stacked so as to form a group G1 of the corrugated board boxes. The corrugated board sheet S of the bottom of the supply part is fed individually from the supply part A to a flexo-printing machine B in which four colors in total (at least two ink colors) are printed on the corrugated board sheet S one color at a time, and the printed corrugated board sheet S is transferred to a slotter•creaser C which performs the creasing and slotting steps in a plurality of places on the corrugated board sheet in a traveling direction (four places in FIG. 5) so as to form crease lines c and slots d parallel to the short end of the sheet S and a gluing margin f.
Subsequently, a hole-making step is performed in a die-cut unit D, and in a folding unit D, the gluing margin f is applied glue and folded so as to attach the gluing margin f to the side e joined/attached to the side e, thereby producing a square-tube shaped corrugated board box W. Next, the corrugated board box W in a flat state is transferred to a counter ejector F in which the number of sheets is counted and stacked in the same direction so as to make a group G2 of the corrugated board boxes. Finally, the corrugated board box group G2 is transferred to a binding machine located on a downstream side of the transferring direction by a transferring conveyor so as to bundle the corrugated board boxes ready for shipment.
Conventionally, when producing a board box of a smaller size, a box-producing machine specialized for small boxes is needed as the size of the board sheet is smaller. But the need for producing small board boxes is not very high and the installation cost becomes expensive to install the small-box producing machine and it is inadvisable. Thus, a method is adopted, in which a corrugated board sheet having a size of two board boxes is produced and then the board sheet is cut into two pieces each having a size of one board box.
Patent Document 1 (JP8-500297T published in 1996) discloses a structure of a device of slitting a corrugated paperboard box in which one board box having a size of two boxes is produced and stacked and then cut symmetrically in half crosswise.
Moreover, Patent Document 2 (JP2002-67190A) discloses a structure of a slotter for grooving a corrugated board sheet formed with a size of two board boxes.
These types of box-producing methods have advantages that the production speed is doubled and the production efficiency is enhanced. There is another advantage that small boxes can be made by using the regular box-producing machine, which broadens the objects that the regular box-producing machine can process.
However, in the box-producing method disclosed in Patent Document 1, folding precision of the corrugated board sheet by the folding unit E is important. That is, if the folding of the corrugated board sheet is not performed precisely by the folding unit E, the panels are not folded at a right angle and the flaps that close the top and bottom of the corrugated box become misaligned, which is called fish tail. When the two-box connected corrugated board sheet is cut into two boxes in this state at the cutting line in the center, one board box has misaligned flaps in one direction and the other board box has misaligned flaps in an opposite direction and neither of the produced boxes is qualified as a product.
Therefore, in the box producing process of two-box connected board sheet, it is necessary to produce a corrugated board box while the occurrence of the fish tail is minimized and the precision of box producing is enhanced. Further, according to the cutting method of the Patent Document 1, the cutting position is easily misaligned as a stack of the board boxes each having a size of two boxes is cut all at once. If the stack of the board boxes is not symmetrically cut in half, the neither one of the cut boxes meets the standard size, thereby being disqualified as a product.
Furthermore, when cutting the two-box connected board boxes, paper powder is generated at the section being cut. This can deteriorate the surrounding environment and the paper powder can get in the corrugated board box group G2 having been cut and stacked, thereby reducing the quality of the corrugated board box.